#include<stdio.h>
long fact(long n);
int main()

{
	int m,k;
	scanf("%d %d",&m,&k);
	long a = fact(m);
	long b = fact(k);
	long c = fact(m-k);
	printf("%ld\n",a/(b*c)); 
}
long fact(long n)
{
	if(n==0||n==1)
	{
		return 1;
	}
	return n * fact(n-1);
}
